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February 8, 2006

Premature birth may affect adult personality

by Sam Savage

NEW YORK (Reuters Health) - Young adults who were born very
prematurely tend to be more anxious and prone to depression
than their peers, a new study suggests.

UK researchers found that among 18- and 19-year-olds, those
who were born very prematurely - before the 33rd week of
pregnancy - generally scored higher on a standard measure of
"neuroticism." That is, they were by nature more nervous, moody
and lacking in self-esteem than their peers who were born
full-term.

At the same time, the preterm group scored lower on a
measure of extraversion, the tendency to be outgoing, assertive
and sometimes risk-taking.

The findings, say the study authors, suggest that young
adults born substantially early may be at higher-than-average
risk of developing clinical depression and anxiety disorders.
However, they report in the journal Pediatrics, the results are
only preliminary, and any conclusions about the risk of mental
health disorders "are necessarily speculative."

For their study, Dr. Matthew Allin of King's College London
and his colleagues assessed 108 young men and women who were
born before the 33rd week of pregnancy, along with 67 young
adults who were born at term. A full-term pregnancy lasts about
40 weeks.

All of the study participants completed standard
questionnaires that measure three dimensions of personality:
neuroticism, extraversion and "psychoticism" -- the tendency to
be emotionally cold, aggressive and prone to antisocial
behavior.

Overall, the preterm group had lower extraversion scores
and higher neuroticism scores. The two groups scored similarly,
however, on the measure of psychoticism.

A complex mix of genes and environment goes into forming an
individual's personality, and it's not clear why premature and
full-term children might have general differences in some
traits, according to Allin and his colleagues.

Early injury to the brain could be one factor, they
speculate, as may the influence of parents and peers as the
children grow up. For example, parents of premature babies may
be more protective from early on, which may contribute to the
more cautious, introspective nature seen in these children.

On the other hand, the researchers point out, it's not
clear how important parenting style may be in adult
personality. Studies of twins who were raised separately
suggest that personality has a large genetic component.

It's possible, Allin's team speculates, that premature
children are more likely than others to inherit certain
personality traits. One recent study found that women with high
anxiety levels during pregnancy were at increased risk of
delivering prematurely - which suggests preterm infants might
be more likely to inherit a tendency toward anxiety.